ABB RET670 Commissioning Manual page 251

1MRK 504 165-UEN A
Transformer protection RET670 2.2 IEC
Commissioning manual
Testing functionality by secondary injection
The voltage regulation algorithm then increases (for transformer T2) or
decreases (for transformer T1) the measured voltage by Udi and compares Ui
against the voltage deadband limits U1 and U2 for the purposes of voltage
regulation.
EQUATION2090 V3 EN-US
9. To cause a tap change, the calculated value for circulating current voltage
adjustment must offset the injected quantity for bus voltage U
outside the voltage deadband created by setting UDeadband. Expressed by
equation 113 and equation 114.
(Equation 113)
EQUATION2092 V2 EN-US
(Equation 114)
EQUATION2094 V2 EN-US
Therfore:
× ×
Ci Icc i Xi U _
EQUATION2096 V1 EN-US
(
-
U 2
>
Icc i _
EQUATION2098 V1 EN-US
10. Using the settings for USet, UDeadband, C (Compensating factor) and Xr2
(transformer short circuit impedance) calculate the magnitude of Icc_i
necessary to cause a tap change command.
11. Inject current equal to I2Base for Transformer 1 and (I2Base - |Icc_i|) for
Transformer 2 so that the magnitude of calculated circulating current will
cause a raise command to be issued for Transformer 2 and a lower command
for Transformer 1. Magnitude and direction of circulating currents measured
for each transformer can be observed as service values on the local HMI and
raise/lower commands detected from the binary output mapped in the Signal
Matrix.
(for the purposes of this test procedure)
> -
2 Uset
)
Uset
( )
×
Ci Xi
Section 11
(Equation 112)
so that Ui is
B
(Equation 115)
(Equation 116)
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